Pattern Detection and Location Indication for a Visual Prosthesis

ABSTRACT

The present invention is generally directed to visual neural stimulation and more specifically to improved usability of a visual prosthesis, and a visual prosthesis structure easily adaptable to the eye or the brain. They system includes a pattern recognition component, and zoom component combined with an indication component for indicating the location of the pattern, such as a face, in a zoomed out image.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claim priority to, benefit of, and incorporates byreference, U.S. Provisional Application 62/036,463, filed Aug. 12, 2014for Visual Prosthesis.

FIELD OF THE INVENTION

The present invention is generally directed to improved usability of avisual prosthesis, and more specifically to pattern detection for avisual prosthesis.

BACKGROUND OF THE INVENTION

Detection and Tacking of Faces in Real Environments by R. Herpers et.al. from International Workshop on Recognition, Analysis and Tracking ofFaces and Gestures in Real-Time Systems, 1999, IEEE Proceedingsdescribes basics of facial detection and recognition software forgeneral applications.

Xuming He presented an ARVO poster in 2011 describing a system for avisual prosthesis that automatically zooms in on a face in a visualscene to help a visual prosthesis user identify the face.

U.S. Patent Application 20080058894 for Audio-tactile VisionSubstitution System to Dewhurst describes providing visual informationto a vision impaired person using audio or tactile information includinginformation regarding facial characteristics.

International patent application WO 20010384465 for Object Tracking forArtificial Vision by Barns et al. describes a system for trackingobjects, such as a face for a visually impaired user.

US Patent application 20130035742 for Face Detection Tracking andRecognition for a Visual Prosthesis, the disclosure of which isincorporated herein by reference, is by the present applicants anddescribes a system for identifying a face and indicating is location tothe user of a visual prosthesis.

SUMMARY OF THE INVENTION

The present invention is generally directed to visual neural stimulationand more specifically to improved usability of a visual prosthesis, anda visual prosthesis structure easily adaptable to the eye or the brain.They system includes a pattern detection and recognition component, andzoom component combined with an indication component for indicating thelocation of the pattern, such as a face, in a zoomed out image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an photograph of an electrode array on a retina showing the20 degree field of view covered by the electrode array.

FIG. 1B is an experimental face detection setup as seen through thecamera of a visual prosthesis with a 53 degree field of view.

FIG. 2A is an experimental face detection setup as seen through thecamera of a visual prosthesis, showing the narrower field of view to theelectrode array, and the electrodes stimulated by a face detectionfilter.

FIG. 2B is an experimental face detection setup as seen through thecamera of a visual prosthesis, showing the wider field of view of thecamera mapped to the electrode array, and the electrodes stimulated by aface detection filter.

FIG. 3 is a flowchart showing facial detection.

FIG. 4 is a set of three flowcharts equating face detection response tosquare localization.

FIG. 5 is a flowchart showing the process of face detection andrecognition.

FIG. 6 is a flowchart showing the process of face cueing.

FIG. 7 is a perspective view of the implanted portion of the preferredvisual prosthesis.

FIG. 8 is a side view of the implanted portion of the preferred visualprosthesis showing the strap fan tail in more detail.

FIG. 9 shows the components of a visual prosthesis fitting system.

FIG. 10 a shows a LOSS OF SYNC mode.

FIG. 10 b shows an exemplary block diagram of the steps taken when VPUdoes not receive back telemetry from the Retinal stimulation system.

FIG. 10 c shows an exemplary block diagram of the steps taken when thesubject is not wearing Glasses.

FIGS. 11-1, 11-2, 11-3 and 11-4 show an exemplary embodiment of a videoprocessing unit. FIG. 11-1 should be viewed at the left of FIG. 11-2.FIG. 11-3 should be viewed at the left of FIG. 11-4. FIGS. 11-1 and 11-2should be viewed on top of FIGS. 11-3 and 11-4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of the best mode presently contemplated forcarrying out the invention. This description is not to be taken in alimiting sense, but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe determined with reference to the claims.

An aspect of the invention is a method of aiding a visual prosthesissubject including detecting a face in the subject's visual scene andcommunicating the location of the detected face including zooming out toshow the location of the detected face through a highlight; andproviding cues to the subject regarding a detected face. The cue mayinclude sound, vibration, stating a name associated with the detectedface, highlighting the detected face, zooming in on the detected face,or tactile feedback. The method may further include looking up thedetected face in a look up table to provide a name associated with thedetected face. The cue may further include an indication of if the faceis looking toward the subject, to the side or looking away. A furtheraspect of the invention is including information about a facialcharacteristic in the cue. Facial characteristics may include gender,size, distance, head movement, or other body motion. All of thesecharacteristics are controllable by the subject through controls on thevideo processing unit worn on the body.

Referring to FIG. 1, The currently available visual prosthesis providesan electrode array 10 which stimulates the retina to provide a field ofview of 20 degrees (FIG. 1A) while a camera 12 provides a 53 degreefield of view (FIG. 1B). While larger arrays are desirable and will beavailable in the future, it is clear that camera technology will alwayssurpass electrode array technology. Zoom system have been provided invisual prostheses. A one to one ratio is best for locomotion and handeye coordination as described in US-2008-0183244-A1, Field of ViewMatching in a Visual Prosthesis. It is also known that zoom in can bebeneficial for task such as reading. However, the facial detection taskbenefits from a wider angle view. It is often beneficial for a visualprosthesis user know the location of faces within a scene. Those facescan be identified with a simple highlight or only stimulating thelocation of the face. It such a case a wider field of view supportsfinding faces quickly. It should be clear that while described inrelation to facial detection any pattern of interest can be detected andit location identified by the same method. Patterns of interest mayinclude, for example, stumble or trip hazards, automobiles, doors,windows or faces.

It is not necessary to zoom the subject's view to detect and identifysuch patterns. In this example, the camera views 53 degrees while only20 degrees is presented to the subjection through an electrode array.Software can be constantly scanning the 53 degree image and notifyingthe user when a pattern of interest is detected in the scene. When apattern of interest is detected, the system can zoom out and cue a user,or cue a user and wait for the user to zoom out manually. It isimportant to not change the field of view without the user's knowledge.

This function can be further combined with recognition functions such aslooking up the a detected face and speaking the name associated with theface. Alternatively the system can describe characteristics of the face.

Referring to FIG. 2, the experimental face detection setup is shown asseen through the camera of a visual prosthesis, showing the narrowerfield of view 2000 to the electrode array 10. A face is detected 2002and electrodes stimulated by a face detection filter 2004. Theadditional information provided by the face detection filter is minimal.A visual prosthesis user will need to scan the scene through the 20degree view until a face is detected. At this level the visualprosthesis user would probably be able to detect a face without thefilter.

Referring to FIG. 2B, the experimental face detection setup is shown asseen through the camera of a visual prosthesis. In this case the widerfield of view of the camera 12 is mapped to the electrode array 10. Aface is detected 2006 by a face detection filter and electrodes arestimulated 2008. With the wider field of view, the visual prosthesisuser is able to identify the location of a face within the scene withminimal or no scanning. Preferably a visual prosthesis user would beable to switch modes quickly and easily. For example, a single buttoncould be provided on the VPU which shifts to the wider field of view andactivating the face detection software. Releasing the button wouldreturn the visual prosthesis to the previous mode. This allows the user,when entering a room for example, to quickly indentify the location offaces in the room.

While described in terms of face detection, the present invention, inparticular as it applies to wide field of view is also applicable towide range of other uses, such as hazard detection. Any item that can bedetected by the visual prosthesis camera and image processing softwarecan be readily identified with the present invention. As anotherexample, when combined with an infrared camera, heat sources can beidentified.

The following table shows face detection response times in a clinicaltrial

Patient ID Wide FOV (53 deg.) Normal FOV (20 deg.) 1 38 ± 4  53 ± 12 220 ± 2 42 ± 5 3  5 ± 1 11 ± 3 4 12 ± 2 22 ± 4The times are in seconds based on 10 trials for each subject after 10practice trials. Another trial was conducted with and without a target(target turned away not showing their face.

Patient ID Mean Response Time 1 5.2 ± .9 2 6.4 ± .7

Referring to FIG. 3, simple face tracking can be a significant benefit ablind person. The presence of multiple faces may be also relayed. Theprocess flow of basic face detection and tracking is provided. The videoprocessor records a visual scene 102, show here with two faces. Thevideo processor draws a square around a detected face 104. The videoprocessor draws squares around both face units and draws a smallersquare around the identifiable portions of the two faces for recognitionprocessing 106. Even with a very low resolution electrode array, it ispossible for a subject to locate the faces 108, to improve interactionwith the other people.

Referring to FIG. 4, square localization is a common task preformed byvisual prosthesis patients. See US Patent Application 2010/0249878, forVisual Prosthesis Fitting Training and Assessment System and Method,filed Mar. 26, 2010 which is incorporated herein by reference. Providinga square over a detected face, simplifies the face tracking to the levela square localization. In the first example 110, the face is indentifiedat an angle. It may be advantageous to straighten the square to improveuser recognition. In the second example 112 the face is outside thevisual scene so no highlight is provided. In the third example 114, theface square is simply highlighted without modification. The distance tothe person, distance direction and velocity may also be relayed to thepatent.

Referring to FIG. 5, the process of face detection begins by scanningthe input image from the camera for a pattern of face 202. There aremany well known processes for indentifying faces in an image. If a faceis detected, it is compared to a database of known faces 204. If theface is unknown, the face is cued 208 as described in greater detail inFIG. 6. If the face is known, it is announced 206. Finally facialcharacteristics are determined 210.

Referring to FIG. 6, there are several options for cueing the presenceof an unknown face which are selectable by the user. The user can changethe selection by activating controls on the VPU 20. The systemdetermines if face highlighting is selected 302, and highlights the face304. In a low resolution visual prosthesis this can be accomplishedsimply replacing the face with a bright image. In a higher resolutionvisual prosthesis this may be accomplished by marking a square or circlearound the face. Alternatively if Zoom is selected 306, the visualprosthesis zooms in on the face adding the user in indentifying the face308, or zooming out to provide the location of the face. If vibration isselected 310 the visual processing unit vibrates (like a cell phone insilent mode) 312. If tone is selected 314, the speaker on the visualprosthesis emits a tone 316. Note that the cues may be used incombination such as highlight, vibrate and tone.

FIGS. 7 and 8 present the general structure of a visual prosthesis usedin implementing the invention.

FIG. 7 shows a perspective view of the implanted portion of thepreferred visual prosthesis. A flexible circuit 1 includes a flexiblecircuit electrode array 10 which is mounted by a retinal tack (notshown) or similar means to the epiretinal surface. The flexible circuitelectrode array 10 is electrically coupled by a flexible circuit cable12, which pierces the sclera and is electrically coupled to anelectronics package 14, external to the sclera.

The electronics package 14 is electrically coupled to a secondaryinductive coil 16. Preferably the secondary inductive coil 16 is madefrom wound wire. Alternatively, the secondary inductive coil 16 may bemade from a flexible circuit polymer sandwich with wire traces depositedbetween layers of flexible circuit polymer. The secondary inductive coilreceives power and data from a primary inductive coil 17, which isexternal to the body. The electronics package 14 and secondary inductivecoil 16 are held together by the molded body 18. The molded body 18holds the electronics package 14 and secondary inductive coil 16 end toend. The secondary inductive coil 16 is placed around the electronicspackage 14 in the molded body 18. The molded body 18 holds the secondaryinductive coil 16 and electronics package 14 in the end to endorientation and minimizes the thickness or height above the sclera ofthe entire device. The molded body 18 may also include suture tabs 20.The molded body 18 narrows to form a strap 22 which surrounds the scleraand holds the molded body 18, secondary inductive coil 16, andelectronics package 14 in place. The molded body 18, suture tabs 20 andstrap 22 are preferably an integrated unit made of silicone elastomer.Silicone elastomer can be formed in a pre-curved shape to match thecurvature of a typical sclera. However, silicone remains flexible enoughto accommodate implantation and to adapt to variations in the curvatureof an individual sclera. The secondary inductive coil 16 and molded body18 are preferably oval shaped. A strap 22 can better support an ovalshaped coil. It should be noted that the entire implant is attached toand supported by the sclera. An eye moves constantly. The eye moves toscan a scene and also has a jitter motion to improve acuity. Even thoughsuch motion is useless in the blind, it often continues long after aperson has lost their sight. By placing the device under the rectusmuscles with the electronics package in an area of fatty tissue betweenthe rectus muscles, eye motion does not cause any flexing which mightfatigue, and eventually damage, the device.

FIG. 8 shows a side view of the implanted portion of the visualprosthesis, in particular, emphasizing the fan tail 24. When implantingthe visual prosthesis, it is necessary to pass the strap 22 under theeye muscles to surround the sclera. The secondary inductive coil 16 andmolded body 18 must also follow the strap 22 under the lateral rectusmuscle on the side of the sclera. The implanted portion of the visualprosthesis is very delicate. It is easy to tear the molded body 18 orbreak wires in the secondary inductive coil 16. In order to allow themolded body 18 to slide smoothly under the lateral rectus muscle, themolded body 18 is shaped in the form of a fan tail 24 on the endopposite the electronics package 14. The strap 22 further includes ahook 28 the aids the surgeon in passing the strap under the rectusmuscles.

Referring to FIG. 9, a Fitting System (FS) may be used to configure andoptimize the visual prosthesis (3) of the Retinal Stimulation System(1).

The Fitting System may comprise custom software with a graphical userinterface (GUI) running on a dedicated laptop computer (10). Within theFitting System are modules for performing diagnostic checks of theimplant, loading and executing video configuration files, viewingelectrode voltage waveforms, and aiding in conducting psychophysicalexperiments. A video module can be used to download a videoconfiguration file to a Video Processing Unit (VPU) (20) and store it innon-volatile memory to control various aspects of video configuration,e.g. the spatial relationship between the video input and theelectrodes. The software can also load a previously used videoconfiguration file from the VPU (20) for adjustment.

The Fitting System can be connected to the Psychophysical Test System(PTS), located for example on a dedicated laptop (30), in order to runpsychophysical experiments. In psychophysics mode, the Fitting Systemenables individual electrode control, permitting clinicians to constructtest stimuli with control over current amplitude, pulse-width, andfrequency of the stimulation. In addition, the psychophysics moduleallows the clinician to record subject responses. The PTS may include acollection of standard psychophysics experiments developed using forexample MATLAB (MathWorks) software and other tools to allow theclinicians to develop customized psychophysics experiment scripts.

Any time stimulation is sent to the VPU (20), the stimulation parametersare checked to ensure that maximum charge per phase limits, chargebalance, and power limitations are met before the test stimuli are sentto the VPU (20) to make certain that stimulation is safe.

Using the psychophysics module, important perceptual parameters such asperceptual threshold, maximum comfort level, and spatial location ofpercepts may be reliably measured.

Based on these perceptual parameters, the fitting software enablescustom configuration of the transformation between video image andspatio-temporal electrode stimulation parameters in an effort tooptimize the effectiveness of the visual prosthesis for each subject.

The Fitting System laptop (10) is connected to the VPU (20) using anoptically isolated serial connection adapter (40). Because it isoptically isolated, the serial connection adapter (40) assures that noelectric leakage current can flow from the Fitting System laptop (10).

As shown in FIG. 9, the following components may be used with theFitting System according to the present disclosure. A Video ProcessingUnit (VPU) (20) for the subject being tested, a Charged Battery (25) forVPU (20), Glasses (5), a Fitting System (FS) Laptop (10), aPsychophysical Test System (PTS) Laptop (30), a PTS CD (not shown), aCommunication Adapter (CA) (40), a USB Drive (Security) (not shown), aUSB Drive (Transfer) (not shown), a USB Drive (Video Settings) (notshown), a Patient Input Device (RF Tablet) (50), a further Patient InputDevice (Jog Dial) (55), Glasses Cable (15), CA-VPU Cable (70), CFS-CACable (45), CFS-PTS Cable (46), Four (4) Port USB Hub (47), Mouse (60),LED Test Array (80), Archival USB Drive (49), an Isolation Transformer(not shown), adapter cables (not shown), and an External Monitor (notshown).

The external components of the Fitting System according to the presentdisclosure may be configured as follows. The battery (25) is connectedwith the VPU (20). The PTS Laptop (30) is connected to FS Laptop (10)using the CFS-PTS Cable (46). The PTS Laptop (30) and FS Laptop (10) areplugged into the Isolation Transformer (not shown) using the AdapterCables (not shown). The Isolation Transformer is plugged into the walloutlet. The four (4) Port USB Hub (47) is connected to the FS laptop(10) at the USB port. The mouse (60) and the two Patient Input Devices(50) and (55) are connected to four (4) Port USB Hubs (47). The FSlaptop (10) is connected to the Communication Adapter (CA) (40) usingthe CFS-CA Cable (45). The CA (40) is connected to the VPU (20) usingthe CA-VPU Cable (70). The Glasses (5) are connected to the VPU (20)using the Glasses Cable (15).

Stand-Alone Mode

Referring to FIG. 10, in the stand-alone mode, the video camera 13, onthe glasses 5, captures a video image that is sent to the VPU 20. TheVPU 20 processes the image from the camera 13 and transforms it intoelectrical stimulation patterns that are transmitted to the externalcoil 17. The external coil 17 sends the electrical stimulation patternsand power via radio-frequency (RF) telemetry to the implanted retinalstimulation system. The internal coil 16 of the retinal stimulationsystem receives the RF commands from the external coil 17 and transmitsthem to the electronics package 14 that in turn delivers stimulation tothe retina via the electrode array 10. Additionally, the retinalstimulation system may communicate safety and operational status back tothe VPU 20 by transmitting RF telemetry from the internal coil 16 to theexternal coil 17. The visual prosthesis apparatus may be configured toelectrically activate the retinal stimulation system only when it ispowered by the VPU 20 through the external coil 17. The stand-alone modemay be used for clinical testing and/or at-home use by the subject.

Communication Mode

The communication mode may be used for diagnostic testing,psychophysical testing, patient fitting and downloading of stimulationsettings to the VPU 20 before transmitting data from the VPU 20 to theretinal stimulation system as is done for example in the stand-alonemode described above. Referring to FIG. 9, in the communication mode,the VPU 20 is connected to the Fitting System laptop 21 using cables 70,45 and the optically isolated serial connection adapter 40. In thismode, laptop 21 generated stimuli may be presented to the subject andprogramming parameters may be adjusted and downloaded to the VPU 20. ThePsychophysical Test System (PTS) laptop 30 connected to the FittingSystem laptop 21 may also be utilized to perform more sophisticatedtesting and analysis as fully described in the related application U.S.Pat. No. 8,271,091, (Applicant's Docket No. S401-USA) which isincorporated herein by reference in its entirety.

In one embodiment, the functionality of the retinal stimulation systemcan also be tested pre-operatively and intra-operatively (i.e. beforeoperation and during operation) by using an external coil 17, withoutthe glasses 5, placed in close proximity to the retinal stimulationsystem. The coil 17 may communicate the status of the retinalstimulation system to the VPU 20 that is connected to the Fitting Systemlaptop 21 as shown in FIG. 9.

As discussed above, the VPU 20 processes the image from the camera 13and transforms the image into electrical stimulation patterns for theretinal stimulation system. Filters such as edge detection filters maybe applied to the electrical stimulation patterns for example by the VPU20 to generate, for example, a stimulation pattern based on filteredvideo data that the VPU 20 turns into stimulation data for the retinalstimulation system. The images may then be reduced in resolution using adownscaling filter. In one exemplary embodiment, the resolution of theimage may be reduced to match the number of electrodes in the electrodearray 10 of the retinal stimulation system. That is, if the electrodearray has, for example, sixty electrodes, the image may be reduced to asixty channel resolution. After the reduction in resolution, the imageis mapped to stimulation intensity using for example a look-up tablethat has been derived from testing of individual subjects. Then, the VPU20 transmits the stimulation parameters via forward telemetry to theretinal stimulation system in frames that may employ a cyclic redundancycheck (CRC) error detection scheme.

In one exemplary embodiment, the VPU 20 may be configured to allow thesubject/patient i) to turn the visual prosthesis apparatus on and off,ii) to manually adjust settings, and iii) to provide power and data tothe retinal stimulation system. Referring again to FIGS. 1 through 4,the VPU 20 may comprise a case, and button 6 including power button forturning the VPU 20 on and off, setting button, zoom buttons forcontrolling the camera 13, temple extensions 8 for connecting to theGlasses 5, a connector port for connecting to the laptop 21 through theconnection adapter 40, indicator lights (not shown) on the VPU 20 orglasses 5 to give visual indication of operating status of the system,the rechargeable battery (not shown) for powering the VPU 20, batterylatch (not shown) for locking the battery in the case, digital circuitboards (not shown), and a speaker (not shown) to provide audible alertsto indicate various operational conditions of the system. Because theVPU 20 is used and operated by a person with minimal or no vision, thebuttons on the VPU 20 may be differently shaped and/or have specialmarkings to help the user identify the functionality of the buttonwithout having to look at it.

In one embodiment, the indicator lights may indicate that the VPU 20 isgoing through system start-up diagnostic testing when the one or moreindicator lights are blinking fast (more then once per second) and aregreen in color. The indicator lights may indicate that the VPU 20 isoperating normally when the one or more indicator lights are blinkingonce per second and are green in color. The indicator lights mayindicate that the retinal stimulation system has a problem that wasdetected by the VPU 20 at start-up diagnostic when the one or moreindicator lights are blinking for example once per five second and aregreen in color. The indicator lights may indicate that there is a lossof communication between the retinal stimulation system and the externalcoil 17 due to the movement or removal of Glasses 5 while the system isoperational or if the VPU 20 detects a problem with the retinalstimulation system and shuts off power to the retinal stimulation systemwhen the one or more indicator lights are always on and are orangecolor. One skilled in the art would appreciate that other colors andblinking patterns can be used to give visual indication of operatingstatus of the system without departing from the spirit and scope of theinvention.

In one embodiment, a single short beep from the speaker (not shown) maybe used to indicate that one of the buttons 6 have been pressed. Asingle beep followed by two more beeps from the speaker (not shown) maybe used to indicate that VPU 20 is turned off. Two beeps from thespeaker (not shown) may be used to indicate that VPU 20 is starting up.Three beeps from the speaker (not shown) may be used to indicate that anerror has occurred and the VPU 20 is about to shut down automatically.As would be clear to one skilled in the art, different periodic beepingmay also be used to indicate a low battery voltage warning, that thereis a problem with the video signal, and/or there is a loss ofcommunication between the retinal stimulation system and the externalcoil 17. One skilled in the art would appreciate that other sounds canbe used to give audio indication of operating status of the systemwithout departing from the spirit and scope of the invention. Forexample, the beeps may be replaced by an actual prerecorded voiceindicating operating status of the system.

In one exemplary embodiment, the VPU 20 is in constant communicationwith the retinal stimulation system through forward and backwardtelemetry. In this document, the forward telemetry refers totransmission from VPU 20 to the retinal stimulation system and thebackward telemetry refers to transmissions from the Retinal stimulationsystem to the VPU 20. During the initial setup, the VPU 20 may transmitnull frames (containing no stimulation information) until the VPU 20synchronizes with the Retinal stimulation system via the back telemetry.In one embodiment, an audio alarm may be used to indicate whenever thesynchronization has been lost.

In order to supply power and data to the Retinal stimulation system, theVPU 20 may drive the external coil 17, for example, with a 3 MHz signal.To protect the subject, the retinal stimulation system may comprise afailure detection circuit to detect direct current leakage and to notifythe VPU 20 through back telemetry so that the visual prosthesisapparatus can be shut down.

The forward telemetry data (transmitted for example at 122.76 kHz) maybe modulated onto the exemplary 3 MHz carrier using Amplitude ShiftKeying (ASK), while the back telemetry data (transmitted for example at3.8 kHz) may be modulated using Frequency Shift Keying (FSK) with, forexample, 442 kHz and 457 kHz. The theoretical bit error rates can becalculated for both the ASK and FSK scheme assuming a ratio of signal tonoise (SNR). The system disclosed in the present disclosure can bereasonably expected to see bit error rates of 10-5 on forward telemetryand 10-3 on back telemetry. These errors may be caught more than 99.998%of the time by both an ASIC hardware telemetry error detection algorithmand the VPU's firmware. For the forward telemetry, this is due to thefact that a 16-bit cyclic redundancy check (CRC) is calculated for every1024 bits sent to the ASIC within electronics package 14 of the RetinalStimulation System. The ASIC of the Retinal Stimulation System verifiesthis CRC and handles corrupt data by entering a non-stimulating ‘safe’state and reporting that a telemetry error was detected to the VPU 20via back telemetry. During the ‘safe’ mode, the VPU 20 may attempt toreturn the implant to an operating state. This recovery may be on theorder of milliseconds. The back telemetry words are checked for a 16-bitheader and a single parity bit. For further protection against corruptdata being misread, the back telemetry is only checked for header andparity if it is recognized as properly encoded Bi-phase Mark Encoded(BPM) data. If the VPU 20 detects invalid back telemetry data, the VPU20 immediately changes mode to a ‘safe’ mode where the RetinalStimulation System is reset and the VPU 20 only sends non-stimulatingdata frames. Back telemetry errors cannot cause the VPU 20 to doanything that would be unsafe.

The response to errors detected in data transmitted by VPU 20 may beginat the ASIC of the Retinal Stimulation System. The Retinal StimulationSystem may be constantly checking the headers and CRCs of incoming dataframes. If either the header or CRC check fails, the ASIC of the RetinalStimulation System may enter a mode called LOSS OF SYNC 950, shown inFIG. 10 a. In LOSS OF SYNC mode 950, the Retinal Stimulation System willno longer produce a stimulation output, even if commanded to do so bythe VPU 20. This cessation of stimulation occurs after the end of thestimulation frame in which the LOSS OF SYNC mode 950 is entered, thusavoiding the possibility of unbalanced pulses not completingstimulation. If the Retinal Stimulation System remains in a LOSS OF SYNCmode 950 for 1 second or more (for example, caused by successive errorsin data transmitted by VPU 20), the ASIC of the Retinal StimulationSystem disconnects the power lines to the stimulation pulse drivers.This eliminates the possibility of any leakage from the power supply ina prolonged LOSS OF SYNC mode 950. From the LOSS OF SYNC mode 950, theRetinal Stimulation System will not re-enter a stimulating mode until ithas been properly initialized with valid data transmitted by the VPU 20.

In addition, the VPU 20 may also take action when notified of the LOSSOF SYNC mode 950. As soon as the Retinal Stimulation System enters theLOSS OF SYNC mode 950, the Retinal Stimulation System reports this factto the VPU 20 through back telemetry. When the VPU 20 detects that theRetinal Stimulation System is in LOSS OF SYNC mode 950, the VPU 20 maystart to send ‘safe’ data frames to the Retinal Stimulation System.‘Safe’ data is data in which no stimulation output is programmed and thepower to the stimulation drivers is also programmed to be off. The VPU20 will not send data frames to the Retinal Stimulation System withstimulation commands until the VPU 20 first receives back telemetry fromthe Retinal Stimulation System indicating that the Retinal StimulationSystem has exited the LOSS OF SYNC mode 950. After several unsuccessfulretries by the VPU 20 to take the implant out of LOSS OF SYNC mode 950,the VPU 20 will enter a Low Power Mode (described below) in which theimplant is only powered for a very short time. In this time, the VPU 20checks the status of the implant. If the implant continues to report aLOSS OF SYNC mode 950, the VPU 20 turns power off to the RetinalStimulation System and tries again later. Since there is no possibilityof the implant electronics causing damage when it is not powered, thismode is considered very safe.

Due to an unwanted electromagnetic interference (EMI) or electrostaticdischarge (ESD) event the VPU 20 data, specifically the VPU firmwarecode, in RAM can potentially get corrupted and may cause the VPU 20firmware to freeze. As a result, the VPU 20 firmware will stop resettingthe hardware watchdog circuit, which may cause the system to reset. Thiswill cause the watchdog timer to expire causing a system reset in, forexample, less than 2.25 seconds. Upon recovering from the reset, the VPU20 firmware logs the event and shuts itself down. VPU 20 will not allowsystem usage after this occurs once. This prevents the VPU 20 code fromfreezing for extended periods of time and hence reduces the probabilityof the VPU sending invalid data frames to the implant.

Supplying power to the Retinal stimulation system can be a significantportion of the VPU 20's total power consumption. When the Retinalstimulation system is not within receiving range to receive either poweror data from the VPU 20, the power used by the VPU 20 is wasted.

Power delivered to the Retinal stimulation system may be dependent onthe orientation of the coils 17 and 16. The power delivered to theRetinal stimulation system may be controlled, for example, via the VPU20 every 16.6 ms. The Retinal stimulation system may report how muchpower it receives and the VPU 20 may adjust the power supply voltage ofthe RF driver to maintain a required power level on the Retinalstimulation system. Two types of power loss may occur: 1) long term (>˜1second) and 2) short term (<˜1 second). The long term power loss may becaused, for example, by a subject removing the Glasses 5.

In one exemplary embodiment, the Low Power Mode may be implemented tosave power for VPU 20. The Low Power Mode may be entered, for example,anytime the VPU 20 does not receive back telemetry from the Retinalstimulation system. Upon entry to the Low Power Mode, the VPU 20 turnsoff power to the Retinal stimulation system. After that, andperiodically, the VPU 20 turns power back on to the Retinal stimulationsystem for an amount of time just long enough for the presence of theRetinal stimulation system to be recognized via its back telemetry. Ifthe Retinal stimulation system is not immediately recognized, thecontroller again shuts off power to the Retinal stimulation system. Inthis way, the controller ‘polls’ for the passive Retinal stimulationsystem and a significant reduction in power used is seen when theRetinal stimulation system is too far away from its controller device.FIG. 10 b depicts an exemplary block diagram 900 of the steps taken whenthe VPU 20 does not receive back telemetry from the Retinal stimulationsystem. If the VPU 20 receives back telemetry from the Retinalstimulation system (output “YES” of step 901), the Retinal stimulationsystem may be provided with power and data (step 906). If the VPU 20does not receive back telemetry from the Retinal stimulation system(output “NO” of step 901), the power to the Retinal stimulation systemmay be turned off. After some amount of time, power to the Retinalstimulation system may be turned on again for enough time to determineif the Retinal stimulation system is again transmitting back telemetry(step 903). If the Retinal stimulation system is again transmitting backtelemetry (step 904), the Retinal stimulation system is provided withpower and data (step 906). If the Retinal stimulation system is nottransmitting back telemetry (step 904), the power to the Retinalstimulation system may again be turned off for a predetermined amount oftime (step 905) and the process may be repeated until the Retinalstimulation system is again transmitting back telemetry.

In another exemplary embodiment, the Low Power Mode may be enteredwhenever the subject is not wearing the Glasses 5. In one example, theGlasses 5 may contain a capacitive touch sensor (not shown) to providethe VPU 20 digital information regarding whether or not the Glasses 5are being worn by the subject. In this example, the Low Power Mode maybe entered whenever the capacitive touch sensor detects that the subjectis not wearing the Glasses 5. That is, if the subject removes theGlasses 5, the VPU 20 will shut off power to the external coil 17. Assoon as the Glasses 5 are put back on, the VPU 20 will resume poweringthe external coil 17. FIG. 10 c depicts an exemplary block diagram 910of the steps taken when the capacitive touch sensor detects that thesubject is not wearing the Glasses 5. If the subject is wearing Glasses5 (step 911), the Retinal stimulation system is provided with power anddata (step 913). If the subject is not wearing Glasses 5 (step 911), thepower to the Retinal stimulation system is turned off (step 912) and theprocess is repeated until the subject is wearing Glasses 5.

One exemplary embodiment of the VPU 20 is shown in FIG. 11. The VPU 20may comprise: a Power Supply, a Distribution and Monitoring Circuit(PSDM) 1005, a Reset Circuit 1010, a System Main Clock (SMC) source (notshown), a Video Preprocessor Clock (VPC) source (not shown), a DigitalSignal Processor (DSP) 1020, Video Preprocessor Data Interface 1025, aVideo Preprocessor 1075, an I²C Protocol Controller 1030, a ComplexProgrammable Logic device (CPLD) (not shown), a Forward TelemetryController (FTC) 1035, a Back Telemetry Controller (BTC) 1040,Input/Output Ports 1045, Memory Devices like a Parallel Flash Memory(PFM) 1050 and a Serial Flash Memory (SFM) 1055, a Real Time Clock 1060,an RF Voltage and Current Monitoring Circuit (VIMC) (not shown), aspeaker and/or a buzzer, an RF receiver 1065, and an RF transmitter1070.

The Power Supply, Distribution and Monitoring Circuit (PSDM) 1005 mayregulate a variable battery voltage to several stable voltages thatapply to components of the VPU 20. The Power Supply, Distribution andMonitoring Circuit (PSDM) 1005 may also provide low battery monitoringand depleted battery system cutoff. The Reset Circuit 1010 may havereset inputs 1011 that are able to invoke system level rest. Forexample, the reset inputs 1011 may be from a manual push-button reset, awatchdog timer expiration, and/or firmware based shutdown. The SystemMain Clock (SMC) source is a clock source for DSP 1020 and CPLD. TheVideo Preprocessor Clock (VPC) source is a clock source for the VideoProcessor. The DSP 1020 may act as the central processing unit of theVPU 20. The DSP 1020 may communicate with the rest of the components ofthe VPU 20 through parallel and serial interfaces. The Video Processor1075 may convert the NTSC signal from the camera 13 into a down-scaledresolution digital image format. The Video Processor 1075 may comprise avideo decoder (not shown) for converting the NTSC signal intohigh-resolution digitized image and a video scaler (not shown) forscaling down the high-resolution digitized image from the video decoderto an intermediate digitized image resolution. The video decoder may becomposed of an Analog Input Processing, Chrominance and LuminanceProcessing and Brightness Contrast and Saturation (BSC) Controlcircuits. The video scaler may be composed of Acquisition control,Pre-scaler, BSC-control, Line Buffer and Output Interface. The I²CProtocol Controller 1030 may serve as a link between the DSP 1020 andthe I²C bus. The I²C Protocol Controller 1030 may be able to convert theparallel bus interface of the DSP 1020 to the I²C protocol bus or viceversa. The I²C Protocol Controller 1030 may also be connected to theVideo Processor 1075 and the Real Time Clock 1060. The VPDI 1025 maycontain a tri-state machine to shift video data from Video Preprocessor1075 to the DSP 1020. The Forward Telemetry Controller (FTC) 1035 packs1024 bits of forward telemetry data into a forward telemetry frame. TheFTC 1035 retrieves the forward telemetry data from the DSP 1020 andconverts the data from logic level to biphase marked data. The BackTelemetry Controller (BTC) 1040 retrieves the biphase marked data fromthe RF receiver 1065, decodes it, and generates the BFSR, BCLKR and BDRfor the DSP 1020. The Input/Output Ports 1045 provide expanded IOfunctions to access the CPLD on-chip and off-chip devices. The ParallelFlash Memory (PFM) 1050 may be used to store executable code and theSerial Flash Memory (SFM) 1055 may provide Serial Port Interface (SPI)for data storage. The VIMC may be used to sample and monitor RFtransmitter 1070 current and voltage in order to monitor the integritystatus of the retinal stimulation system.

Accordingly, what has been shown is an improved visual prosthesis. Whilethe invention has been described by means of specific embodiments andapplications thereof, it is understood that numerous modifications andvariations could be made thereto by those skilled in the art withoutdeparting from the spirit and scope of the invention. It is therefore tobe understood that within the scope of the claims, the invention may bepracticed otherwise than as specifically described herein.

What we claim is:
 1. A visual prosthesis comprising: a camera suitableto be external to the body; a video processing unit receiving video datafrom the camera and producing stimulation codes indicating electrodepatterns to be presented; the video processing unit including a zoomcomponent and a pattern detection component; a wireless transmitterreceiving codes from the video processing unit and transmitting thecodes; an implantable wireless receiver suitable to be implanted withina body receiving the codes from the wireless transmitter; an implantablesignal generator receiving the codes from the wireless receiver andgenerating stimulation signals; an implantable electrode array receivingthe stimulation signals and suitable to stimulate visual neural tissuewherein the zoom component and the pattern detection component areoperable to together to zoom out and provide an indication of thelocation of a pattern in a zoomed out image.
 2. The visual prosthesisaccording to claim 1, wherein the pattern detection component detectsfaces.
 3. The visual prosthesis according to claim 1, wherein thepattern detection component detects hazards.
 4. The visual prosthesisaccording to claim 1, wherein the zoom component and pattern detectioncomponent are manually operable.
 5. The visual prosthesis according toclaim 1, wherein the pattern detection component is continuous and cuesa user to manually operate the zoom component.
 6. The visual prosthesisaccording to claim 1, wherein the pattern detection component iscontinuous and automatically activates the zoom component in response toa detected pattern.
 7. The visual prosthesis according to claim 6,wherein the visual prosthesis cues a user in response to the zoomcomponent being automatically activated.
 8. The visual prosthesisaccording to claim 1, further comprising a pattern recognition componentrecognizing features of the detected pattern.
 9. The visual prosthesisaccording to claim 8, wherein the pattern recognition component includesa look up table of patterns and identifying information.
 10. The visualprosthesis according to claim 9, wherein the look up table associatesfaces with names.
 11. The visual prosthesis according to claim 10,further comprising an enunciator to announce to a name associated with adetected face.